Zinc Iodide-osmium Tetroxide Impregnation Research Articles

Structure and Function of the Root Cap of Lolium temulentumL. (Poaceae): Parallels with the Ligule

Structure of the root cap of Lolium temulentumL. and of the chemistry of its secretory product were investigated with conventional transmission electron microscopy, zinc iodide–osmium tetroxide impregnation, and use of protein and polysaccharide localization techniques at the ultrastructural level. Structural and functional information concerning the root cap is compared with that previously obtained for the membranous ligule of this species. Similarities between root cap cells and adaxial epidermal cells of the ligule are described and discussed. It is concluded that both systems are secretory and represent a similar response to the common problem of easing the passage of growing organs against the soil or other plant parts.

Structure and Function in the Grass Ligule: the Endomembrane System of the Adaxial Epidermis of the Membranous Ligule of Lolium temulentum L. (Poaceae)

The endomembrane system of the adaxial epidermal cells of the membranous ligule of the grass Lolium temulentum L. has been studied by conventional transmission electron microscopy, and by using zinc iodide-osmium tetroxide impregnation with examination of thick sections at 100 kV. The components of the endomembrane system are the nuclear membranes, rough endoplasmic reticulum (present in both cisternal and tubular forms), dictyosomes, dictyosome-derived vesicles, coated vesicles, plasma membrane and tonoplast. Direct continuity between tubular endoplasmic reticulum and the cis face of dictyosomes is demonstrated and the applicability of the endomembrane concept to this putative secretory tissue is discussed. The presence of vesicle-like profiles apparently within the outer tangential walls is reported.

Zinc iodide-osmium tetroxide impregnation of the "tubulo-vesicular system" in Tomes' process of the rat incisor ameloblast.

Zinc iodide-osmium tetroxide (ZIO) is a nonspecific but selective impregnation method that visualizes a tubulo-vesicular system in cells. The detailed structure and three-dimensional distribution of this ZIO-impregnated system was studied in the Tomes' process of secretory ameloblasts in the rat incisor. The ZIO-impregnated system consisted of an extensive array of smooth membrane-bound thick and thin tubules and vesicles. The interconnected thick and thin tubules formed a complex "core network" in the central cytoplasm of Tomes' process that enmeshed and often surrounded individual secretory granules. From the core network, radial branches extended toward the smooth cell membrane of the interdigitating portion of Tomes' process. Although the core network and branches frequently appeared connected to the secretory granules and the cell membrane, stereo-pair electron microscopy failed to show conclusive evidence of such continuity. However, many coated vesiclelike structures were attached to the core network and its branches. No special relationship was found between interrod and rod secretory sites and the tubulo-vesicular network. In thick sections, the ZIO-impregnated tubulo-vesicular network occupied a considerable volume of cytoplasm. The vinblastine-labile nature of this network as demonstrated previously (Nanci et al., 1987) indicated that the system undergoes rapid and extensive turnover. Considering the dynamic nature and sheer volume of the tubulo-vesicular system, we propose that it be regarded as a major cell organelle.

Ultracytochemical evidence for the presence of GERL in pinealocytes of the Mongolian gerbil (Meriones unguiculatus).

Ultracytochemical reactions for the demonstration of acid phosphatase, glucose-6-phosphatase and thiamine pyrophosphatase, as well as zinc iodide-osmium tetroxide impregnation, revealed the existence of GERL (Golgi apparatus-Endoplasmic Reticulum-Lysosomes) in pinealocytes of the Mongolian gerbil (Meriones unguiculatus). The spatial arrangement of this structure was studied on thick sections using a goniometric stage. Although it was not possible to determine whether GERL in pinealocytes belongs to the Golgi apparatus or to endoplasmic reticulum, it can be concluded that its presence in studied cells signifies that they are considerably more active synthetically than has been believed to date.

Synaptic and Synaptoid Vesicles Constitute a Single Category of Inclusions. New Evidence From ZIO Impregnation

Parallel observations on central synaptic and neurohaemal terminals of the same types of neurosecretory fibres in the polychaete annelid Nereis diversicolor reveal that their respective populations of inclusions exhibit identical, highly distinctive patterns of affinity for the zinc iodide-osmium tetroxide (ZIO) reagent. The method highlights the duality of possible secretory inclusions in nerve terminals. Many typical synaptic/synaptoid vesicles have ZIO-positive contents, but intermingle with unreactive vesicles. Both positively and negatively reacting vesicles contribute to the unusual dense clusters associated with sites of release of neurochemical mediators, characteristic of polychaete nervous systems. Fewer dense-cored synaptic/synaptoid vesicles have reactive cores. The larger ‘storage granules’ typically have unreactive contents, but dense deposits form within a small minority. A possible cytophysical, in contradistinction from a cytochemical, basis of affinity for ZIO is discussed. The results further support the postulated fundamental identity of synaptic and synaptoid vesicles.

Cell Reactivity Pattern of the Guinea Pig Cecal Mucosa Evidenced by the ZIO Technique

The zinc iodide-osmium tetroxide (ZIO) technique is presently employed to study both, neural and non neural tissues. Precipitates depends on cell types and possibly cell metabol ism as well.Guinea pig cecal mucosa, already known to be composed of epithelium with cells at different maturation stages and lamina propria which i s formed by morphologically and functionally heterogeneous cell population, was studied to determine the pat tern of ZIO impregnation. For this, adult Guinea pg cecal mucosa was fixed with buffered 1.2 5% g 1 utara 1 dehyde before incubation with ZIO for 16 hours, a t 4°C in the dark. Further steps involved a quick sample dehydration in graded ethanols, embedding in Epon 812 and sectioning to observe the unstained material under a phase contrast light microscope (LM) and a transmission electron microscope (TEM).

Comparative aspects of nervous control of pars intermedia

The comparative study of pars intermedia control clearly indicates that both nerve and blood supplies are essential pathways for the control of MSH release. Most of the blood vessels penetrating the pars intermedia of tetrapods derive from a dense vascular plexus interposed between the neural and intermediate lobes. In many species this plexus intermedius represents the only vascular supply to the pars intermedia. In turn, this plexus is supplied by capillaries draining the neural lobe, and in some species, also by capillaries coming from the median eminence. Therefore, the blood irrigating the pars intermedia comes from two important neurohemal areas. Based on histochemical and ultrastructural characteristics more than one type of nerve fiber has been described in the pars intermedia of most species studied. The application of the zinc iodide-osmium tetroxide impregnation method (ZIO) to the pars intermedia showed that all types of nerve fibers have ZIO-positive material. Several histochemical, pharmacological and experimental studies strongly suggest that certain variations of the ZIO method and the histochemical fluorescence methods for biogenic amines stain the same group of substances. It is, therefore, postulated that all pars intermedia nerve fibers contain a biogenic amine. Consequently, the distinction between “ordinary” and catecholamine-containing fibers in the pars intermedia should be reconsidered. Instead, the different types of fibers of the pars intermedia may be recognized by considering their histochemical, ultrastructural and electrophysiological characteristics, or their different origins. In lower vertebrates the pars intermedia is poorly vascularized and richly innervated. On the contrary, the innervation of the pars intermedia of higher vertebrates is poor or completely absent and blood vessels are more numerous. However, the pars intermedia of most species studied appears to be under hypothalamic inhibitory control, regardless of the pattern of innervation. All the evidence available points to the possibility that the purely nervous mechanism inhibiting MSH release in lower vertebrates has shifted to a neurovascular mechanism in higher vertebrates.

Selective zinc iodide-osmium tetroxide impregnation of synaptoid vesicles in the rat neurohypophysis

Selective zinc iodide-osmium tetroxide impregnation of synaptoid vesicles in the rat neurohypophysis

Zinc iodide-osmium tetroxide impregnation of nerve terminals in the spinal cord

Summary The zinc iodide-osmium tetroxide (ZIO) stain of synaptic vesicles has been improved by combining it with aldehyde prefixation. The method used by Martin et al. in cephalopod nerves has been adapted for mammalian tissues. All nerve terminals of spinal grey matter of adult rats were found to contain ZIO-positive vesicles. Both S-type and F-type synaptic vesicles were stained, although approximately half of the vesicular population remained unstained. Aside from staining synaptic vesicles the ZIO method brings out the structural difference between F-type and S-type boutons very clearly and might prove useful in systematic studies concerning the distribution of these two types of synapses throughout the nervous system. The problem of specificity of ZIO staining reaction and its relationship to cholinergic transmission mechanisms still remains to be solved.

Application of the zinc iodide-osmium tetroxide impregnation of synaptic vesicles in cephalopod nerves

The zinc iodide-osmium tetroxide (ZIO) method has been modified to include glutaraldehyde perfusion and fixation prior to the reaction for staining synaptic vesicles. This has resulted in better preservation of structure in the giant fibre system of Loligo vulgaris, and in the optic lobe of Octopus vulgaris. In the squid second to third order giant synapse most of the vesicles (400–600Ådiameter) remained electron transparent after reaction. Those in afferent synaptic boutons ending on the first order giant axons of the palliovisceral lobe became electron opaque. The method can therefore discriminate between vesicles which are clear and of the same shape and size in normal electron microscopy. In the neuropil of the Octopus optic lobe the majority of normally clear vesicles (300–600Ådiameter) became electron opaque after reaction. The dense core vesicles (800–1300Ådiameter) did not show reaction. The frequency of different types of vesicles and endings has been estimated. The majority of terminals examined contained mixed populations of vesicles. The reaction was also obtained in isolated synaptosomes. The specificity of the reaction and the implications of the results are discussed.